Bacterial gummosis

Managemenr of Bacterial Gummosis in Temperate Fruits

1. BACTERIAL GUMMOSIS OR CANKER SUBMITTED TO: DR BHUPESH GUPTA SUBMITTED BY: RAJAT SHARMA (H-2017-67-M)

2. INTRODUCTION Bacterial canker caused by Pseudomonas syringae pv . syringae P.syringae pv . persicae causes disease symptoms on peach and bacterial decline on nectarine, peach and Japanese plum. Bacterial canker is also known as gummosis , because it causes gumming in infected trees and also as blossom blast , because it causes blackened wilted blossoms in the spring.

3. BACTERIAL CANKER is caused by the bacterial pathogen Pseudomonas syringae pv syringae . Bacterial canker is a disease of the stems and leaves of Prunus , especially plums and cherries, but also apricots, peaches and ornamental  Prunus  species. Symptoms: stems and spurs:  Sunken, dead areas of bark develop in spring and early summer, often accompanied by a gummy ooze. If the infection spreads all round the branch it will die rapidly On leaves:  Small brown spots appear which are often round and fall out later to leave holes – as if the leaf had been hit by shotgun pellets, leading to the popular name of ‘ shothole ’.

4. SYMPTOMATOLOGY Gummosis is a general, nonspecific condition of stone fruits (peach, nectarine, plum and cherry) in which gum is exuded and deposited on the bark of trees. Gum is produced in response to any type of wound, regardless of whether it is due to insects, mechanical injury or disease. Gummosis most commonly occurs as a result of perennial canker, bacterial canker and the peach tree borer. Gummosis can also be associated with certain viruses, adverse growing sites, winter damage, herbicide damage and many other factors.

5. Cankers gradually enlarge until infected limbs are girdled and then die. Gummosis is usually associated with the cankers. The canker fungi overwinter in active cankers in living wood or in dead wood. Infection occurs where the bark is damaged or injured. Infection following cold injury frequently occurs in the crotch angles of affected trees.

6. EVIDENT GUMMOSIS CANKER ON SHOOT

7. In Peach, Apricot and Nectarine: Damaged areas are slightly sunken and somewhat darker in color than surrounding bark. Cankers have a soured smell. The bacterium is a weak pathogen and causes serious damage only when a tree is in a near dormant condition or weakened due to unfavorable growing conditions.

8. In Plum: Cankers develop at the base of infected buds on trunk and scaffold limbs. In Cherry: Disease outbreaks are sporadic and more frequent on sweet cherry than on sour cherry. The foliage becomes yellow, curled, and withered. Wet spring weather can result in shoot blight and a small angular leaf spot. This is usually only a problem in young orchards.

9. DISEASE CYCLE Pseudomonas syringae  survives in or on plant surfaces, is spread by splashing rain, and is favored by high moisture and low temperatures in spring. The disease is worse in low or sandy spots in the orchard. Vigorous trees are less susceptible to bacterial canker. Young trees, 2 to 8 years old, are most affected. The disease rarely occurs in first year of planting and is uncommon in nurseries.

10. MANAGEMENT STRATEGIES Several factors must be taken into consideration: Orchard sites should not have acidic or sandy soils; Trees should be purchased from nurseries known to be free of bacterial canker; Rootstock and cultivar selections should be appropriate for the geographical area; Tree vigour should be maintained by using proper fertilization and irrigation practices; And trees should be pruned to limit chance of spread by pruning in early summer rather than winter.

11. MANAGEMENT Planting trees that are budded or grafted about 32 inches above the root crown can help suppress bacterial canker infections. Bacterial canker tends to mostly affect weak trees, so any management practice that improves tree vigour (e.g., lighter, more frequent irrigation, improved tree nutrition, nematode management, etc.) will help to reduce the incidence of this disease. Trees on Lovell peach rootstock are more resistant than others; those on plum rootstocks are most susceptible. Delayed pruning may help. In light sandy soils and some heavy soils, successful control has been achieved with preplant fumigation for nematodes. Application of copper during dormancy has not been shown to protect against bacterial canker.

12. CHEMICAL CONTROL Chemical control of bacterial canker is based on sprays with fixed copper or Bordeaux mixture in autumn and in spring before blossoming. Copper sprays protect initial infection but cannot prevent the canker phase, once infection has occurred. Lovell peach rootstocks are more tolerant to bacterial canker than most other peach rootstocks. ‘ Windsor ’, and ‘ Hardy Giant ’ sweet cherry cultivars are susceptible and should be avoided in disease prone areas. Cherry rootstocks considered resistant to bacterial canker are F12-1 and Mazzard.

13. Nematodes stress trees, which predisposes them to bacterial canker. Preplant fumigation for nematode control reduces the severity of bacterial canker in newly planted orchards. The benefits of preplant soil fumigation for control of bacterial canker usually lasts only a few years; in some areas only limited improvements in disease control occur following soil fumigation.

14. RECOMMENDATION In Plum : Avoid using high fertilizer rates in late summer. Trees showing signs of bacterial canker should be left and pruned after all other trees have been completed. In peach, apricot and nectarine :Avoid using high nitrogen fertilizer rates in mid to late summer. Prune when the trees are fully dormant (January and February). High dosage of a copper containing fungicide at leaf drop has been somewhat successful. In Cherry: Use resistant F12-1 Mazzard rootstock. Remove girdled branches. Spray with copper hydroxide in October and January.

15. During pruning, do not leave stubs and avoid a very close flush cut. Do not leave weak-angled crotches when shaping trees as these are potential sites of infection. Apply Mashobra paste after cleaning the wounds at the time of dormancy break. Spray Streptocycline (20g/100l) before the onset of rainy season. Spray Blitox-50 (0.3%) after leaf fall.